1. Field of the Invention
The invention relates to the field of converting digital data representing figures or objects into a pixel-like display for use in a pattern generator.
2. Prior Art
The present invention has its origin in the generation of patterns used in the fabrication of integrated circuits. With today's very large scale integrated circuits, hundreds of thousands of transistors are fabricated on a single die. Each layer of the circuit may require upwards of millions of figures (such as rectangles, triangles, etc.) to define circuit elements such as gate structures, diffusion patterns, interconnects and others. Numerous technologies are available for generating these patterns for the fabrication of masks or for directly exposing photoresist on a semiconductor wafer. Electron beam lithography, for instance, is one technology currently in use for generating patterns.
The rasterizer of the present invention receives data representing figures or objects and then provides the pixel-like representation of the figures. The pixel memories are scanned and their outputs used to control laser beams which themselves scan a workpiece, such as a photoresist layer or a semiconductor reticle. Because of the millions of bytes required to define even a single die of a complex circuit, prior art methods for generating patterns on a real time basis are too slow or too costly. As will be seen, the present invention provides an apparatus for rapidly and efficiently providing such patterns.
The rasterizer of the present invention is based on an 8.times.8 array which takes advantage of the architecture found in many commercially available dynamic random-access memories. The closest prior art known to Applicant is described in "The 8.times.8 Display", ACM Transactions on Graphics, Vol. 2, No. 1, January 1983, pages 32-56 by Sproull, Sutherland, Thompson, Gupta, and Winter. As will be seen, the present invention provides faster, more efficient processing through unique circuitry over that described in this article.